(a) Field of the Invention
The present invention concerns techniques of pulsed combustion where a flame of a burner of an industrial furnace which is supplied with fuel and an oxidant is provided with a pulsation, to cause cyclic variations of at least one of the flows of fuel and oxidant which feeds the burner.
(b) Description of Prior Art
Already known are processes of pulsating combustion, based on the principle of increasing the volume of burned gases. This volume increase acts on devices for controlling the flows of the gases to be burned by causing a decrease of the combustion, and therefore, a decrease of the volume of the burned gases. The upstream pressure of the fluids then reestablishes the flows at their highest value and the combustion increases, thus ensuring a pulsating combustion.
Such a process is described in the document EP-A-0.046.898.
The document SU-A-857.642 describes a device for pulsating air for the combustion of gaseous or liquid fuels which operates on the principle of a paddle wheel mounted on an axis.
It is known that the production of nitrogen oxide, which is harmful to the environment, depends on partial pressures of oxygen, nitrogen, as well as on the temperature of the medium, which is a problem in the case of pure oxygen which is increasingly used in industrial furnaces because of the numerous advantages that it provides. Studies made by the Applicant have shown that, for example, in the case of pure oxygen, the content of nitrogen oxide fumes increases from 180 ppm to 1600 ppm in a so-called adiabatic furnace of 25 KW, where the thermic energy is transmitted to the walls of the furnace and to the fumes produced as a function of a content of nitrogen in the natural gas varying from 2 to 16%. Similarly, the content of nitrogen oxides in the fumes increases from 150 ppm to 500 ppm in a furnace, for example, a furnace for melting glass, where the thermic energy is simultaneously transmitted to the charge, to the walls and to the fumes, as a function of the content of nitrogen in the natural gas used. The Applicant has, on the other hand, observed that, all things being equal, the content of nitrogen oxides in the fumes goes from 700 ppm to 1200 ppm when the content of residual oxygen in the fumes goes from 1% to 4%.